Conventionally, the coverage area of a wireless communication network such as, for example, a Time Division Duplex (TDD), Frequency Division Duplex (FDD) Wireless-Fidelity (Wi-Fi), Worldwide Interoperability for Microwave Access (Wi-max), Cellular, Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), or 3G based wireless network can be increased by a repeater. Exemplary repeaters include, for example, frequency translating repeaters or same frequency repeaters which operate in the physical layer or data link layer as defined by the Open Systems Interconnection Basic Reference Model (OSI Model).
A physical layer repeater designed to operate within, for example, a TDD based wireless network such as Wi-max, generally includes antenna modules and repeater circuitry for simultaneously transmitting and receiving TDD packets. Preferably, the antennas for receiving and transmitting as well as the repeater circuitry are included within the same package in order to achieve manufacturing cost reductions, ease of installation, or the like. This is particularly the case when the repeater is intended for use by a consumer as a residential or small office based device where form factor and ease of installation is a critical consideration. In such a device, one antenna or set of antennas usually face, for example, a base station, access point, gateway, or another antenna or set of antennas facing a subscriber device.
For any repeater which receives and transmits simultaneously, the isolation between the receiving and transmitting antennas is a critical factor in the overall performance of the repeater. This is the case whether repeating to the same frequency or repeating to a different frequency. That is, if the receiver and the transmitter antennas are not isolated properly, the performance of the repeater can significantly deteriorate. Generally, the gain of the repeater cannot be greater than the isolation to prevent repeater oscillation or initial de-sensitization. Isolation is generally achieved by physical separation, antenna patterns, or polarization. For frequency translating repeaters, additional isolation may be achieved utilizing band pass filtering, but the antenna isolation generally remains a limiting factor in the repeater's performance due to unwanted noise and out of band emissions from the transmitter being received in the receiving antenna's in-band frequency range. The antenna isolation from the receiver to transmitter is an even more critical problem with repeaters operating on the same frequencies and the band pass filtering does not provide additional isolation.
The same issues pertain to frequency translation repeaters, in which receive and transmit channels are isolated using a frequency detection and translation method, thereby allowing two Wireless Local Area Network (WLAN) IEEE 802.11 units to communicate by translating packets associated with one device at a first frequency channel to a second frequency channel used by a second device. The frequency translation repeater may be configured to monitor both channels for transmissions and, when a transmission is detected, translate the received signal at the first frequency to the other channel, where it is transmitted at the second frequency. Problems can occur when the power level from the transmitter incident on the front end of the receiver is too high, thereby causing inter-modulation distortion, which results in so called “spectral re-growth.” In some cases, the inter-modulation distortion can fall in-band to the desired received signal, thereby resulting in a jamming effect or de-sensitization of the receiver. This effectively reduces the isolation achieved due to frequency translation and filtering.
Further, in a WLAN environment utilizing the proposed IEEE 802.11n standard protocol, wireless devices rely on multi-path transmissions to increase data rates and range. However, in a typical home WLAN environment, multi-path transmission capability and spatial diversity are limited for many of the same reasons discussed above in connection with lack of performance of wireless products in a home or indoor environment.